9.20 M.I.T. 2013 Lecture #27 Sociobiology and Culture 1 John Alcock, The Triumph of Sociobiology, ch 8: What is the brain, really? 1. Explain the statement (p 150), that “the brain is essentially a reproductive organ....” 2 John Alcock, The Triumph of Sociobiology, ch 8: What is the brain, really? 1. Explain the statement (p 150), that “the brain is essentially a reproductive organ....” Like every other organ or mechanism that living things are born with, since they have evolved largely by the processes of natural selection—based on the maximal transmission of genes. 3 John Alcock, The Triumph of Sociobiology, ch 8: A thought experiment: the consequences of blank slate brains 2. What would the long-range evolutionary outcome be if, at a given time, most people had “blank slate” brains at birth? p 153 4 John Alcock, The Triumph of Sociobiology, ch 8: A thought experiment: the consequences of blank slate brains 2. What would the long-range evolutionary outcome be if, at a given time, most people had “blank slate” brains at birth? p 153 They would be taken advantage of – exploited – by variants who had more targeted brains. With genetic variation, the totally blank-slate individuals would decrease and disappear. Noam Chomsky: "The blank slate brain is a dictator's dream." 5 John Alcock, The Triumph of Sociobiology, ch 8: Conditional strategies [Review from Scott book] 3. Conditional strategies are common in humans. Give an example of a conditional strategy in an insect, showing that insect behavior is not always rigidly pre- programmed. p 156-159 6 John Alcock, The Triumph of Sociobiology, ch 8: Conditional strategies 3. Conditional strategies are common in humans. Give an example of a conditional strategy in an insect, showing that insect behavior is not always rigidly pre-programmed. p 156-159 A Rove beetle in Costa Rica, L. versicolor is a dung beetle that feeds on flies. Large males are territorial, with larger jaws. Smaller males mimic female behavior and are courted by the larger males; while being courted, they can catch flies and mate with females. The same males change to male behavior in different situations. 7 Rove beetles Courtesy of Andreas Kay on Flickr. License CC BY-NC-SA. Courtesy of Ken-ichi Ueda on Flickr. License CC BY-NC. 8 John Alcock, The Triumph of Sociobiology, ch 8: Conditional strategies Be sure to note that individuals following one or another mating strategy are probably not different genetically. The underlying genes could be the same, but could code for the development of conditional strategies. 9 John Alcock, The Triumph of Sociobiology, ch 8: Types of learning as specific adaptations [Review from Scott book] 4. Learning mechanisms have evolved in order to increase fitness – to increase the likelihood that an individual’s genes will be reproduced. As a result, these mechanisms are less general than many They are specific to learning theorists have claimed. different situations. Give an example, from the learning of ingestion- related behavior in rats as studied by John Garcia. p 162 10 John Alcock, The Triumph of Sociobiology, ch 8: Types of learning as specific adaptations 4. Learning mechanisms have evolved in order to increase fitness – to increase the likelihood that an individual’s genes will be reproduced. As a result, these mechanisms are less general than many learning theorists have claimed. Give an example, from the learning of ingestion-related behavior in rats as studied by John Garcia. p 162 Skinner’s “universal laws” of reinforcement learning are violated in the poisoned bait effect. (How is this kind of learning See earlier discussion of Scott’s book. Class 16. different?) Also, note that different kinds of negative reinforcement have very different consequences in the learning of food preferences, studied in rats: • Electric shock to the skin after ingestion has little effect on future preferences. • X-ray exposure that makes the rat feel sick after it eats or drinks something results in avoidance of the substance subsequently. 11 John Alcock, The Triumph of Sociobiology, ch 8: Channeled nature of learning abilities 5. Give two or three examples of the channeled nature of learning abilities in humans. Are there similar special abilities in animals? p 167f, 171-173 12 John Alcock, The Triumph of Sociobiology, ch 8: Channeled nature of learning abilities Humans: . Language acquisition . Anticipation of the actions of others with a sense of others’ intentions based on what we attend to and learn. Learning of faces for later recognition . Which of these abilities are shared with other animals, especially primates? Animals: . Bird song learning (as studied in white-crowned sparrows and in zebra finches) . Finding specific places by birds that cache food supplies (also done by mice and some other animals) . Maze learning by rats, adapted to living in complex tunnels . Etc. 13 Why do humans engage in behaviors that seem to reduce their fitness? • They may not really reduce fitness; they are Darwinian puzzles. Sociobiologists attempt to solve them. – Keep in mind that behaviors that evolved to increase fitness may no longer do so in greatly altered environments. • Examples: – Pet love (previously discussed); A preference probably evolved because alcohol was present in ripe – Alcoholism fruits, which are healthy to eat. – Acts of altruism: studied by Robert Trivers (1985) and by Richard Alexander (1987): reciprocal altruism, and the value of a reputation for charitability – Use of spices? (next question) – Voluntary reductions in family size; the demographic transition (question 7) 14 John Alcock, The Triumph of Sociobiology, ch 8: The use of spices as a Darwinian puzzle 6. The use of spices in cooking seems at first to be a human luxury with no particular adaptive value, and thus their widespread use, and the great value placed on spices in human history, presented a Darwinian puzzle. What adaptive value of spices has been proposed and supported by data? p 177-179 15 John Alcock, The Triumph of Sociobiology, ch 8: The use of spices as a Darwinian puzzle 6. The use of spices in cooking seems at first to be a human luxury with no particular adaptive value, and thus their widespread use, and the great value placed on spices in human history, presented a Darwinian puzzle. What adaptive value of spices has been proposed and supported by data? p 177-179 Anti-microbial properties. Hence, used more in hot climates. See p 179 figure. Also note: East African practices by Maasai and Batemi. They use plant additives in milk that lower cholesterol (saponins, phenolics) 16 John Alcock, The Triumph of Sociobiology, ch 8: The demographic transition 7. Define the “demographic transition” in human populations. It presents a Darwinian puzzle, for which the proposed solutions are incomplete. See p 183 figure. Note that a decline in average fertility began in several European countries in the late 1800s, and in a few others in the early 1900s. Thus, it began before the development of modern birth control methods. 17 John Alcock, The Triumph of Sociobiology, ch 8: The demographic transition Observed reduction in female fertility: Are there fitness advantages? – Evolutionary advantages of timing of pregnancies – Advantages of acquiring wealth to pass on to children, grandchildren – Omitted in text: Effects of overcrowding, which include, in animal studies, reduction in fertility. – Also of great importance: Humans evolved under conditions of limited communication and relatively small group sizes. Rapid long distance communication and awareness of population sizes and their consequences is very recent in evolutionary time. Read Alcock’s discussion of how traits that had evolved to improve genetic fitness have resulted in reduced genetic fitness in wealthier people, not only because of modern contraceptive methods but also because of societal legal restrictions. 18 John Alcock, The Triumph of Sociobiology, ch 8: Sociobiology and rape 8. See Appendix, Q1 about rape “Barbara Ehrenreich says that because the children sired by rapists in the past surely were more likely to die than those of paternal nonrapists, rape cannot possible be an evolved adaptation [Time, 2000]. Is she correct? Why might she make this claim?” 19 John Alcock, The Triumph of Sociobiology, ch 8: Sociobiology and rape 8. See Appendix, Q1 about rape Actually 2/3 do not fail to ejaculate, so sociobiological explanations are not refuted. “Barbara Ehrenreich says that because the children sired by rapists in the past surely were more likely to die than those of paternal nonrapists, rape cannot possible be an evolved adaptation [Time, 2000]. Is she correct? Why might she make this claim?” Not a good argument because many do survive. She may make the claim because she does not want anyone to consider rape as “natural” behavior. 20 Is rape a “natural” behavior? • It is practiced only by a small minority of men, hence it is not natural in the usual sense. • In some species, forced copulation is more widespread. • However, it becomes more common in humans under certain conditions, as in wartime conquests. (Thus, it could be considered to be a “conditional strategy”—however abhorrent this seems.) 21 John Alcock, The Triumph of Sociobiology, ch 8: Testing a cultural determinism hypothesis 9. See Appendix, ch 8, Q2 about parental care/ How could you test this hypothesis? 22 John Alcock, The Triumph of Sociobiology, ch 8: Testing a cultural determinism hypothesis How could you test this hypothesis? (Are all male- female differences in parental care learned?) Cross-culture studies. Why is it that nearly all cultures are similar in this? Twin studies: Are variations in parental care genetically influenced? Deliberate attempts by caregivers to influence children… 23 John Alcock, The Triumph of Sociobiology, ch 8: Explaining reactions against sociobiologists’ hypotheses 10.